Lock In Amplifier Circuit

The typical lock in amplifier the block diagram of a typical lock in amplifier is shown in figure 3.

Lock in amplifier circuit.

Virtually all lock in amplifiers are able to synchronize with an external reference signal. At the same time a photoresistor op amp circuit is used to detect the light from this led. Pre amplifier reference generator low pass filter input output multiplier output amplifier. Although optimized for operation up to 1 khz the circuit is useful at frequencies up to several hundred kilohertz.

Depending on the dynamic reserve of the instrument signals up to 1 million times smaller than noise components potentially fairly close by in frequency can still be reliably detected. The input amplifier a synchronous demodulator and a final low pass filter amplifier that finally outputs our dc signal. Ignor ance is a valuable asset. Readers should be aware that the following discussion makes no assumptions as to the technology used to implement each of the circuit elements and that analog mixed technology and digital methods may be used.

Low q notches were made max. Equipment multiplier li output modulation li input s n schematic i the principal components of the lock in are. A lock in amplifier is an amplifier that can lock in on a specific signal reference input while ignoring everything else. The vco also contains a phase shifting circuit that allows the user to shift its signal from 0 360 degrees with respect to the reference.

Components of a lock in amplifier a block diagram of a lock in amplifier is shown in the figure. Also the function generator is connected directly to the lock in amplifier so the lock in knows what signal frequency it should be looking for. The output of this circuit is monitored on both an oscilloscope and the lock in amplifier. The phase sensitive detector is a circuit which takes in two voltages as inputs v1 and v2.

In most cases like in the present one a sine generator as the reference source is built in. Line in option in sr510 for hum removal. Notch to remove hum for building a lock in amplifier which is itself a very high q notch. We can break down the lock in amplifier in this instructable into three parts.

The input amplifier ad620 amplifies the input signal using a variable gain resistor. 1 a multiplier 2 an rc circuit low pass filter or integrator 3 a phase shifting circuit. Time constant reference signal phase shifter sine generator r c gain sig. In a world of constant bombardment with noise and distraction the ability to ignore something i e.

Bandwidth was very high of the order of 100khz q w b w. Depth of 28 8db and using ad620 as op amp instead of ua741 for high precision. Each of the elements can be constructed using a simple integrated circuit.